Current understanding in the regulation of gonadotropin secretion and the kin similarities between humans and the Rh-monkeys suggests that inquiries into the role of hypothalamic catecholamines (CA's) and LRF and the detailed analyses in the operative characteristics of the pituitary gonadotrophs should yield critical knowledge regarding the integrated function of the hypothalamic-hypophyseal-ovarian system. Through the use of sensitive and specific methods, morphological organization (histochemical and immunohistochemical) and quantitative distribution of dopamine and norepinephrine (enzymatic-isotopic measurement) and LRF (radioimmunosassay) in the hypothalamus, its specific nuclei (microdissection), pituitary, cerebrospinal fluid as well as in peripheral blood will be measured. Studies will be conducted in the RH-monkey and in humans when feasible. Determinations will be made under normal conditions (including puberty, menstrual cycle and at menopause) and also following estrogen, progesterone and pharmacological manipulations. The mode of gonadotropin release as related to estrogen and progesterone induced changes in the pituitary response to constant LRF infusion or to pulses of LRF will be measured in humans as a means of determining changes in "sensitivity" of the gonadotrophs. The overall objective of the proposed research is to establish the functional relationship between hypothalamic CA's and LRF and the feedback modulation by ovarian steroids in the neuroendocrine control of gonadotropin output in primates.